Add transaction ID column to transactions page

Added ID column as the first column in the transactions table to make it easy to reference transaction IDs when manually mapping receipts. The ID is displayed with a "#" prefix in a small, muted style.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

MoneyMap/Pages/Transactions.cshtml

@@ -140,6 +140,7 @@
                 <table class="table table-hover table-sm mb-0">
                     <thead>
                         <tr>
+                            <th style="width: 70px;">ID</th>
                             <th style="width: 110px;">Date</th>
                             <th>Name</th>
                             <th>Memo</th>
@@ -153,6 +154,7 @@
                         @foreach (var t in Model.Transactions)
                         {
                             <tr>
+                                <td class="small text-muted">#@t.Id</td>
                                 <td>@t.Date.ToString("yyyy-MM-dd")</td>
                                 <td>
                                     <div class="d-flex align-items-center gap-2">